Rory McIlroy and Scottie Scheffler’s drivers failed conformance tests at the PGA Championship. Could YOU be using an illegal driver and not know it?
Could your driver be illegal? It’s a fair question – especially in light of what happened to Rory McIlroy at the 2025 PGA Championship. And the tournament’s winner, Scottie Scheffler.
When McIlroy arrived at Quail Hollow, his game looked sharp and he was a heavy favorite to win the tournament. But on Tuesday his TaylorMade Qi10 driver was ruled non-conforming after a routine inspection. McIlroy did not comment on the situation, and the USGA and PGA of America maintain a policy of not revealing the names of players who fail random equipment tests.
In his post-round press conference Sunday evening, after being asked about his driver by Golfweek’s Adam Schupak, Scheffler confirmed he was forced to make a change before the tournament started as well.
“So the driver testing is something that regularly happens on tour. My driver did fail me this week,” he said. “We had a feeling that it was going to be coming because I’ve used that driver for over a year. I was kind of fortunate for it to last that long.”
McIlroy was forced to use a backup driver head, and while he still made the cut, he struggled to find fairways early on. His situation echoed a similar incident with Xander Schauffele at the 2019 Open Championship, where his driver also failed a conformity test.
The likely cause for both McIlroy and Scheffler’s drivers failing the test was a phenomenon referred to as CT creep. So, what is CT creep, and could it make your driver non-conforming too?
What is CT, and what exactly is CT creep?
In golf equipment terms, CT stands for Characteristic Time. It’s a measurement recorded in microseconds that indicates how long the ball stays in contact with the clubface during impact. Think of it as a scientific way to gauge how “springy” or “hot” a driver face is. The longer the contact time, the more trampoline-like effect the club has, which can translate to higher ball speeds and longer drives.
The USGA and R&A have set a strict limit of 239 microseconds, with a manufacturing tolerance that extends to 257 microseconds.
“CT creep” happens when a driver’s clubface becomes more flexible over time, usually because of repeated use and high-speed impacts. The constant force of striking golf balls – especially by fast swingers such as McIlroy, Scheffler or Schauffele – can cause the metal in the face to subtly fatigue and flex more. Over hundreds or thousands of shots, this can push the CT beyond the legal limit.
How is driver CT tested?
At some PGA Tour events and major championships, the USGA and R&A conduct random CT tests on drivers players intend to use. They use a pendulum-style device that gently strikes the clubface at several spots, measuring how long the face stays in contact with the striker. If any spot exceeds the limit, that driver is deemed non-conforming.
Tests are quick, and most drivers pass without issue. But on occasion, a few fail. Tour players aren’t accused of cheating when this happens – CT creep is understood as normal wear and tear. Still, rules are rules, and after a club crosses the threshold, it’s no longer legal in competition.
CT creep and recreational golfers
Here’s the big question for club golfers: If it can happen to Rory and Scottie and Xander, could it happen to you?
The short answer: probably not.
CT creep is more likely when a driver is used frequently by a high-speed player who consistently strikes the sweet spot. That describes many Tour pros – but not most weekend players. While some amateurs swing fast, few combine tour-level speed, consistency and volume of shots needed to cause CT creep.
That said, drivers used by recreational players can lose performance over time, but that’s usually due to damage – dropping the club on cart paths, shaft/head damage and so on – not an increase in CT that would make the club illegal.
For competitive amateurs who play often and swing fast – college players, elite juniors and long drivers – it’s not impossible, but it remains rare outside professional circles.
Can you get your driver’s CT tested?
Unfortunately, the devices used by the USGA and tours cost thousands of dollars and aren’t publicly available, so you can’t test your driver yourself.
Clubfitters and shops don’t have CT testers either. They can assess general performance using launch monitors (launch, spin, ball speed) but not measure CT precisely.
If you’re seriously concerned – say you’re preparing for a USGA amateur qualifier where testing might happen – contact your club’s PGA professional or your driver’s manufacturer. Some OEMs offer inspections or testing for suspected non-conforming clubs, though don’t expect quick turnaround.
The bottom line on CT creep
CT creep is a byproduct of how close modern drivers come to the legal edge. Manufacturers push performance while staying within the Rules of Golf, meaning some drivers walk a fine line right out of the box.
For most golfers, this is more a “tour story” than a personal concern. You’re unlikely to carry a “too hot” driver unless you’re an elite player with a well-worn gamer that’s seen multiple seasons of use.
In McIlroy and Scheffler’s cases, the failing drivers probably got that way simply from being hit a lot by two of golf’s fastest, most consistent swings. They didn’t cheat or do something to gain an unfair advantage over the field.
For the rest of us, CT creep is a reminder of just how advanced today’s equipment is – and how the rules are enforced at the top level.
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